Support for work-pieces for grinding helical concave surfaces in blades.



C. A. KIRSGHNER. SUPPORT FOR WORK PIECES FOR GRINDING HELIUAL OONOAVE SURFACES IN BLADES.

AIfPLIOATION FILED JAN. 30, 1911.

1,039,294, Patented Sept. 24, 1912.

- in such a manner that the UNITED STATES PATENT OFFICE.

CARL AUGUST KIRSCHNER, OF SOLIN GEN, GERMANY.

SUPPORT FOR WORK-PIECES FOR GRINDING HELIGAL CONCAVE SURFACES IN BLADES.

Specification of Letters Patent.

Patented Sept. 24, 1912.

Application filed January 30, 1911. Serial No. 605,394.

To all whom it may concern:

Be it known that I, CARL AUGUST KIRsoH- NER, engineer, a citizen of Germany, residing in Solingen, in the Province of Rhineland and State of Prussia, Germany, have invented new and useful Improvements in Supports for Work-Pieces for Grinding Helical Concave Surfaces in Blades, of which the following is a specification.

The present invention contemplates a support for work-pieces for grinding helical concave surfaces in blades with which the blade-holder is swung while moving crosswise to the grinding disk around an axis parallel to the sense of the cross-movement. Thus in grinding the cutting surface of scissors blades an edge wound around a straight line is obtained in such a way that the grinding surface is placed as nearly as possible into the axis of oscillation of the blade-holder.

Blade-holders, swinging around an axis parallel to the grinding surface are known already. These,however, are either bladeholders which, at a traverse movement in front of the grind-stone, perform several oscillations, the so-called beating movement, face to be ground turns out to become curved; or, for obtaining helical concave surfaces the grinding face of the blade-holders performs during the cross-movement in front of the grinding stone a vibrating movement around the axis of oscillation; this means that in bladeholders of'the latter description the grinding face is located in front of the axis of oscillation. These known contrivances are not suitable for grinding the blades of scissors. The sinuosity of the concave face at a scissors-blade has the purpose of rinding independently the two cutting ec ges moving toward each other so as to give to the cutting edges all over the whole length of the blades the required utmost precision in cutting. WVhen the axis of rotation of the workpieceholder and consequently that of the workpiece itself has its position outside of the grinding disk and of the grinding face, the

line as corresponds to the extent of swing. Otherwise the sinuosity becomes incongruous and this edge is the more distant from the line of junction the farther, in grinding the cutting edge of scissors, the axis of r0- tation of the workpiece is away from the grinding face. In the same proportion the curvature of this edge of the blade increases, whereas, when the axis of oscillation lies in the grinding face, viz. in its point of intersection with the mentioned line of junction, this edge remains quite straight. The more curved, however, are the blade-edges of scissors moving toward each other, the more the blade-points move asunder on closing same; this means that the operation of the scissors is the rougher toward the point, in proportion as the points are exposed to a shearing stress. Thus scissors will cut the smoother the straighter a blade is ground.

With a view now to obtain a maximum of evenness in scissor-blades, the present invention provides for the axis of rotation of the blade-holder being placed as exactly as possible into the grinding surface; thus in this axis of oscillation the edge of the scissors-blade must remain a straight one, as exposed in the foregoing.

In the accompanying drawing, in which similar letters refer to similar parts throughout the several views, the invention is represented in one form of embodiment.

Figure l is a front view and Fig. 2 a side-view of a grinding contrivance.

a is a grindstone and b a bed on which a sledge a can be guided by means of a prismatic guide toward the grindstone.

(l and e are bearings connected with the sledge o and carrying the grind-support f.

g is the scissors-blade to be ground and its cutting edge is marked by 71,.

The working principle of the invention is as follows :-The axis of oscillation of the grinding support is, as results from the drawing, in the grinding face itself, so that, when the grinding-sup ort f changes its position, the scissors-blace to be ground performs a rotation around its axle. The dislocation of the grinding support takes place during a movement in front of the grindstone invariably in the same sense, z. e. on the whole length of blade by a slight fraction of the whole rotation. By a proper turning device the blade is always given the proper position in front of the grindstone; thus, by displacing the grinding support in its axis of rotation in front of the grindstone, a slightly sinuated concave face must be formed, the generatrix of which 1s at a straight line extending within-the v p of the blade extends substantially along t e groundface, i. efalong the cutting edge.

I claim A device of the character described, com

prising a grinding Wheel, a support arranged in proximity thereto, a slide movable along said support and having a pair ofbearings thecenter of Which extends parallel to the axis ofthe-grinding Wheel and. is adapted Within said bearings and adapted for so supto be alined with the periphery of said Wheel, and a Work holder rotatably mounted 15 porting a scissor-blade that. the cutting ed e axis of the holder, whereby said blade is ground hollow with astraight cutting edge.

(ma AUGUST KIRSGHNER. a. 8.]

Witnesses CHASE J. LWRIGHT, ALFRED HENKEL;

Copies of this patent mav be obtained for five cents each, ibyyaddrcssingthe 1 Commissioner ofi'latents.

Washington, D. 0.? v 

